I'm pretty confident it wasn't due to a secret relationship. He's a digital nomad so he's never in one place for very long, which he'd stated early on as to why he doesn't expect to have a long term relationship with anyone.
So in fairness to him, he did try to manage my expectations. I knew it was a "situationship" and even told myself to not get too invested, just enjoy the moment with him etc and be ready to move on once he left.
I lost sight of that the longer we spent together, and despite what he said at the beginning, I naively thought that things were naturally developing into something more serious and that he'd be willing to do something long distance with me.
But in fairness to me also, he did say things like how he didn't expect that we'd become so close, that I was the first person to make him reconsider moving back to his home country, and he did all kinds of things that imo, most people wouldn't do for someone who's just a casual fling. It's just hard for me to understand that sort of inconsistency, but I guess all I can do is accept that people can be like that and that they'll disappoint you as a result.
I had to quit my job not long ago to recover from burnout, and for some reason I decided to start using Arch btw even though I'm a kind of a linux noob (maybe as a more acceptable form of self-harm) and spent the next month locked away to tinker with it.
My setup is pretty much complete now, so I guess I'll just focus on growing a beard this time. Thanks for the great tips!